This project will examine the action of general anesthetics on the spinal cord input mechanisms. For this purpose cats will be used as experimental animals whose vital signs are kept strictly within physiological normality to differentiate the effects of various side effects of anesthetics from their primary action on the central nervous system. It is proposed to study: 1) Effects of anesthetics on dorsal horn spinal gray laminae and nuclear aggregates utilizing extracellular single unit recording; in particular, a) effects of anesthetics on spontaneous single unit activity, b) effects of anesthetics on single unit activity evoked by peripheral stimulation, 2) Effects of anesthetics on the spinal input control mechanisms; in particular, a) effects of anesthetics on primary afferent depolarization, b) correlation of dorsal root potentials with single unit activity in the dorsal horn spinal laminae.